The use of a “vanishing edge” as a portion of the perimeter of a swimming pool is known. This vanishing edge, also known as a “negative edge” is actually a lip which forms a portion of the edge of the pool. Water within the pool cascades gently over the edge and into a receiving area where the water is recirculated back into the swimming pool. The attractive feature of the negative or vanishing edge is that it is not visible and thus it appears to the user that he is within an infinite body of water since there is no appearance of a retaining wall for the pool constricting the water. It is particularly useful where there is a view that is desirably seen while the user is in the pool or while the user is lounging at the side of the pool because there is no blockage of the view by a visible water retaining edge extending above the water surface.
Heretofore, the feature has not been available in portable hot tubs or spas which are manufactured at a manufacturing location and conveyed to the place of installation. This is so because, whereas with a swimming pool permanently assembled at the place of installation, there was no difficulty with water recirculation to the pool from the overflowing water. The water flowing over the vanishing edge was simply recirculated into the pool circulation system and then outputted into the pool water inlet. Because pools are much larger than hot tubs and hold commensurately much greater quantities of water, the amount of water displaced by a user or users in proportion to the total quantity of water in the pool is relatively small which has no disadvantageous effect on water circulation. However, in hot tubs, the amount of water displaced by a user or user is much greater proportionately than that with a pool. Provisions much be made for overcoming the problem of relatively large amounts of water leaving the hot tub and returning that quantity of water to the hot tub over time. These considerations are difficult to deal with in hot tubs or the like with the result that vanishing edges in hot tubs are not in common use.